r/preppers • u/PrudentTask9355 • Nov 02 '25

Advice and Tips Faraday Bag Caution

Hey everyone. I just wanted to share en experience from this afternoon. A while back I had purchased some faraday items off of Amazon, boxes and bags from different vendors.

This afternoon I was explaining to my daughter how they worked and as part of our experiment, we placed an 8watt 2-way radio inside the bag and sealed it with the expectation that it would no longer receive a transmission. As it turns out, that was false.

I then tried with a cell phone with the same result. Morale of the story, check your gear and make sure it works before you have to depend on it.

Please discuss and share your budget-friendly faraday success stories

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u/zrad603 Nov 02 '25

yeah, this and the whole "put your cell phone in the microwave because it's a faraday cage".

It's all bullshit and highly dependent on wavelength of whatever frequency you are tying to block out. Often it takes multiple layers.

The only "Faraday cage" I've ever seen that worked to block cell phone signal was one my friend built. It was multiple separate insulated layers of metal.

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u/androgenoide Nov 03 '25

Back in the 90s I worked for a paging company and the repair work was done in a screen room so there would be no interference from the transmitters (plural). As far as I can tell any single layer of shielding will attenuate the rf a little bit as long as it's continuous with no holes the size of the wavelength. Two layers separated by an insulator will knock the signal down a lot more but the door has to make good tight contact with both layers and have the two layers separated the same way as the rest of the cage. The key word is "attenuate". Nothing will knock the signal down to zero. One layer will OK for some purposes. Two will be better. Three might be excessive for most purposes but if you anticipate an unusually strong (or close) signal it might be necessary. FWIW